In all of the known practical electrochemical systems involving halogen, elemental halogen is produced or utilized somewhere in the system. This is true for both the reversible electrochemical systems such as the zinc/chlorine battery, and for non-reversible systems such as the sodium chloride chlorine-manufacturing cell.
In the zinc/chlorine battery described, e.g., U.S. Pat. No. 3,713,888, as the battery is charged, the chlorine emerges from the cell as chlorine gas which is then dissolved in water or electrolyte and the latter is then cooled to form chlorine hydrate, in which form the chlorine is stored until the battery is discharged. When the battery is discharged, the chlorine hydrate is decomposed into chlorine gas and water, and the chlorine gas is then dissolved in the cell electrolyte in order to sustain the discharge.
In the sodium chloride chlorine manufacturing process, chlorine gas formed is transferred out of the cell, dried and mechanically compressed and cooled into liquid form for storage and disposal.
The necessity of handling elemental halogen, which is corrosive and toxic, increases the safety hazards inherent in the system, requires the use of high cost corrosion-resistant materials, and reduces the efficiency of the system. It has now been found that the safety, reliability, and efficiency of the system can be increased while at the same time the need for high cost construction materials can be reduced by employing reservoirs with flexible walls. Accordingly, it is the object of this invention to provide a new electrochemical system in which halogen is produced or utilized having increased safety, reliability and efficiency and reduced need of high cost construction materials.